95-843 Service Oriented Architecture          Homework 1

Due: Midnight, Wednesday, July 8, 2009

Fundamental Issues
==================

Read the chapter on Petri nets from the Johnsonbaugh
text (PetriNetIntro.pdf)  and read the article by Hamadi on web 
service composition using Petri nets. Read the BPMN slides from
IBM. All of these are provided on the course schedule.

Submit a Word document or scanned drawings containing your 
answers to the assignment section on blackboard.

Model the following algorithms with a Petri net. Provide a 
marking that represents the situation prior to execution of
the algorithm.

1. A = 1
   B = 2
   C = A + B
   C = C + 1

2. A = 2
   B = A + A
   C = 3
   D = A + A
   C = A + B + C

3.     A = 1
       S = 0
   10  S = S + A
       A = A + 1
       GOTO 10

4. Wash a lion:

   1. Get lion.
   2. Get soap. (real soap not SOAP)
   3. Get tub.
   4. Put water in tub.
   5. Put lion in tub.
   6. Wash lion with soap.
   7. Rinse lion.
   8. Remove lion from tub.
   9. Dry lion.

5. In class we described a set theoretic description 
of Petri nets. Represent the Petri net you drew
in question 4 (Washing the lion) using sets. Show
the sets P, T and E as on slide 24 of the Introductory
slides.

6. Describe the following web service in words: 
   Ref(S1, assess_claim, [A1:An])

7. Prove statement (20) of the Service Algebra studied in class.

8. Prove statement (21) of the Service Algebra studied in class.

9. Wash the lion again. This time use the Business Process Modeling
Notation as described on the slides from IBM. Be sure to exploit
parallel execution where possible.

10. Consider the Expense Reimbursement Process on slide 76 of IBM's
BPMN slides. Briefly describe where the diagram uses parallelism.